Mineral Information and Data:

Bastnasite-(Ce)
CeCO3F [CNMNC approved formula]

Named as the Ce-predominant rare earth element in the bastnasite group. Group named after its locality: Bastnas Mine, Riddarhyttan district, Vastermanland, Sweden. First published in 1841. Name changed from bastnasite per nomenclature of rare-earth minerals (IMA, 1966).

IMA status : Renamed IMA Approved; 1966 ()
CLASSIFICATION 
Dana
(8th edition) :
16a.01.01.01  
  (16a) Carbonates - Hydroxyl or Halogen
  (16a.01) in the Bastnasite/Shynchysite/Parasite Groups
  (16a.01.01) Bastnasite Subgroup
  
Nickel-Strunz
(10th edition) :
05.BD.20a
  (05) Carbonates and Nitrates
  (05.B) Carbonates with additional anions, without H2O
  (05.BD) With rare earth elements (REE)
  
Crystal system: Hexagonal System
Point group (H-M): 6m2 (or 6m2) — ditrigonal-dipyramidal
Space group: P6c2
Unit cell: a = 7.118(1) Å, c = 9.762(1) Å
Crystal Habit: Commonly in tabular to equant crystals, with {0001} and {1010}, may be modified by {1120}, {1011}, {1012}, {1013}, {1122}, horizontally striated, may be elongated, commonly in syntaxic intergrowth with rontgenite-(Ce), synchysite-(Ce), parisite-(Ce), or cordylite-(Ce), to 20 cm; granular, massive.
Twinning: On {1010}, indistinct; {0001}, a parting, distinct to perfect
  
Color: Wax-yellow, honey-yellow, reddish brown; in transmitted light, pale yellow to colorless
Diaphaneity: Transparent to translucent
Luster: Vitreous to greasy, pearly on basal partings
Hardness (Mohs): 4 - 4.5
Measured Density: 4.9 – 5.2 g/cm3
Tenacity: Brittle
Fracture: Uneven
  
Polymorphism and Series: Polytypes: 4H, 6R, 3R;
Forms a series with hydroxylbastnasite-(Ce).
Geologic Setting: The most abundant RE-bearing mineral, typically hydrothermal, although primary igneous occurrences are known. In granite and alkali syenites and pegmatites; in carbonatites; in contact-metamorphic deposits; rarely as a detrital mineral in placers.
Mineral Association: Allanite-(Ce), cerianite-(Ce), synchysite-(Ce), parisite-(Ce), cerite-(Ce), fluocerite-(Ce), fluorite.
  
Other Properties: Gemstone Extremely Rare.

 

Bastnasite-(Ce)
Bastnasite-(Ce) with orthoclase
Origin: Zagi Mountain, North-West Frontier Province, Pakistan
Sample size: 2.6 x 2.8 x 4.4 cm
Photo: Dan Weinrich

 

Bastnasite-(Ce)
(zoom-in of above)

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